introduction to dvb-h
DESCRIPTION
Lecture from Multimedia Broadcast course held in TUTTRANSCRIPT
Digital Video Broadcast for Handheld devicesDVB-H
Multimedia groupAdrian Hornsby
Broadcast Multimedia
10/28/08
Voice communication …
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In 1876, Alexander Graham Bell
"Mr. Watson. Come here! I want you!"
Radio …
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• 1860s, Scottish physicist, James Clerk Maxwell predicted the existence of radio waves
• 1886, German physicist, Heinrich Rudolph Hertz demonstrated that rapid variations of electric current could be projected into space in the form of radio waves.
• 1895 ,Guglielmo Marconi, Italian inventor, sent and received his first radio signal, in 1899 across the English Channel and two years later received the letter "S", from England to Newfoundland.
• Nikola Tesla and Nathan Stufflefield took out patents for wireless radio transmitters. Nikola Tesla is now credited with being the first person to patent radio technology; the Supreme Court overturned Marconi's patent in 1943 in favor of Tesla.
Television …
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• Television started in the 1920s as a Peepshow device. • one viewer , 30 lines, tiny vertical screens, • received in a large part of Europe via the 'short wave', also used for radio.
• Audio sound was a separate short wave radio broadcast.
Personal portable devices…
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Mobile phones …
10/21/08
Users worldwide
Digital Media Revolution …
• New user experience• New consumer demand
10/21/08
New digital devices + new digital transmission systems =
New digital transmission standard
Why did it happen ??
Soon more mobile phones than people ...
TV is the biggest and most popular media ...
... and the last one missing from mobile phones
... something is missing here !!!
How did it all started ...
• Research on DVB-T based mobile application • Is DVB-T good for mobile ?• Should we modify it ?
• Politic pressure – Authorized (TM chairman) secret research late 2000
• DVB-T SE (standard extension) » Jukka Henriksson, Nokia» Report in December 2001 » Adding 4k and inter-leaving» Power consumption known problem but ...
How did it all started ...
• DVB-M (CM) Group formed based on reports– launch in 2002 (Juha Salo, Nokia)
• Requirements accepted by CM mid-2002– Co-existence with Mobile Phones– Indoor scenarios– Single antenna reception– Reduced power consumption
• DVB-M (TM)• Evaluate DVB-T for those requirements
DVB-T in short ...
• December 1995, DVB publish the DVB-T standards (EN 300 744)
•
10/21/08
DVB-T in short ...
• Terrestrial Digital Television Standard
• One-to-many broadband wireless data transport– Video, audio, data (also IP, late addition)
– Scalable (cell size up to 100km)
– Huge capacity (54 channels, 5-32Mbit/s)
• Lead to the ASO (analog switch off)
• MPEG-2 transport stream based (flexible)
• OFDM multi-carrier modulation (2k and 8k mode)
– Carrier modulation QPSK, 16QAM, 64QAM
• All in all, DVB-T is pretty good and flexible
• So what is wrong really ??
DVB-T in short …
• OFDM, multi-carrier modulation (2k and 8k mode)• Each sub-scarrier is modulated with conventionat
schemes (QAM)2k: larger inter-carrier
→ Tolerance Doppler
8k: small inter-carrier
→ large symbole duration
→ maximum echo delays
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Multipaths effect ...
•Different environment, different propagation
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So why not DVB-T ??
• Designed for rooftop reception
• No power saving mechanism
• Inadequate impulse noise protection
How did it all started ...
• DVB-H (TM)– Call for technology (Jan/Feb 2003)– 12 responses– 3 concept formed in April– Final concept in August– Standard accepted by TM in January 2004– By ETSI in the end of 2004
» Now we have a new physical layer standard for mobile devices
How did it all started ...
• DVB-CBMS (TM)– Nokia’s initiative to ‘complete’ the work
• All layers need to be standardized
– 2003: early specifications of the interface to the terminal for early trials
– 2004: detailed technical requirements for an "IPDC in DVB-H" system
• Call for technologies started in autumn 2004• First standards to TM in fall 2005• DVB-IPDC to ETSI in 2006/2007
What really is DVB-H for ??
• DVB-H aims at providing digital TV reception to mobile devices
• Combines traditional TV broadcast standards with element specific to handheld devices– Smaller screen– Mobility– Antennas– Indoor coverage– Reliance on battery power
What is DVB-H ??
• Transmission of data mainly done as IP frames– Internet Protocol
• New video compression scheme (h.264)– For lower bitrate and smaller screen size– Approx. 390 Kbit/s per stream (mpeg2 was 3-4 Mbit/s)
• More suitable for broadcasting to mobile environment
New features of DVB-H ..
• Time-slicing• power saving and frequency handover
• MPE-FEC• additional protection of the data link layer
• New 4k mode: • trade-off between cell size and mobile reception
capability (Doppler and echo delays)
• New signaling scheme• modified TPS bits and additional mpeg PSI/SI
tables (INT)
Time-slicing
Cha
nnel
Cap
acity
Time
Service 1
Service 4
Service 2
Service 3
• In DVB-T, services are multiplexed on the TS level at very high frequency
• Service almost sent in parallel
• Very hard for decoder to only focus on one stream (specific TS packets)
• All data must be received, leading to high power consumption
• 8k, 16QAM ½ 1/8, 11.06Mbit/s• 7412 TS packets/OFDM symbol, 1 symbol = 1008us
• 1 TS packet every 136us
Time-slicingC
hann
elC
apac
ity
Time
• IP service organized so that each services use the full channel capacity one after another– Burst transmission– Seamless frequency handover– Longer initial tunning delay
Off time Bur
st
Time-slicing
• The off-time period provides up to 90% of power saving
• The receiver has to know when the next interesting burst (service being consumed) is arriving
– Real-time signalling
– PSI/SI not sliced
ChannelCapacity Time
Time-slicing
• Time-slicing permits the monitoring of neighboring cells during off-time
• In DVB-T, would need 2 frontends
Cha
nnel
Cap
acity
Time
Off time
Listening to C3Listening to C2
ServingC1
Adj.C2
Adj.C3
MPE-FEC
• Multi-Protocol Encapsulation with Forward Error Correction– Reed-Solomon coding on IP datagrams
• Higher error resistance
– Virtual interleaving, FEC placed in separate sections
– Receiver can ignore FEC sections
RS Codewords
Application data tableIP data
(191 columns)
RS data tableParity Bytes
(64 col.)
1024 rows m
ax
Multi-protocol Encapsulation (MPE)
• IP encapsulation into MPEG-2 TS packets
PayloadHeaderIP datagram
MP sections PayloadHeader PayloadHeader PayloadHeader PayloadHeader
PayloadHeader PayloadHeader PayloadHeader PayloadHeader
40 ... 4080 bytes
16 ... 4095 bytes
188 bytes
TS packets
4k mode
• 4k: 3409 carriers
• Compromised between 2k (1705 ca.) and 8k (6817 ca.)
• Increased mobility by two compared to 8k
• SFN cell size double compared to 2k
• 4k is an option, 2k and 8k can be used for specific environment (rural, dense city)
Signaling with TPS-bits
• Physical layer extensions
• Reserved information channel with tunning parameters (Time-slice, MPE-FEC, Cell ID, ...)
• Very robust signalling scheme allowing TPS lock even with very low C/N values
• Faster to access signalling than demodulating and decoding the PSI/SI or the MPE sections
DVB-H codec
Service Information
• Main difference between DVB-T and DVB-H
• DVB-H does not utilize all the service information table defined by DVB (PSI/SI)
• DVB-H uses IP based Information system, “service guide” rather than the traditional PSI/SI from DVB
Service Guide
• Electronic Service Guide (ESG)– XML based service definition
Service Guide
Service Structure
DVB-H Protocol Stack
DVB-H delivery mechanisms
• File Delivery over Unidirectional Transport (FLUTE) protocol– File download (download first, then consume)
• Real-time Transport Protocol (RTP)– Streaming (consume while downloading)– Without RTCP report (broadcast)
FLUTE
• Asynchronous (non-real time) broadcasting of audio, video, and data files
• Download and store at the receiver for future playback
– IETF RMT WG– RFC 3926
“FLUTE is a protocol for the unidirectional delivery of files over the Internet, which is particularly suited to multicast networks. The specification builds on Asynchronous Layered Coding (ALC), the base protocol designed for massively scalable multicast distribution.”
FLUTE
ABCDA
B
C
D
FDT Receiver
Receiver gets content of the carousel from the FDT
Receiver can select which message to download
FLUTE
Taken from Jani Peltotalo (TUT) /File Delivery over DVB-H, FLUTE
RTP- Real-Time Transport Protocol
• RTP provides end-to-end network delivery services for the transmission of real-time data
• RTP is network and transport-protocol independent, though it is often used over UDP.
RTP- Real-Time Transport Protocol
• Use SDP file extracted from ESG to get tune in and decoding information necessary for the player to understand and decode the RTP stream and its payload
v=0o=QTSS_Play_List 1460227057 502868560 IN IP4 130.230.50.48s=stream32c=IN IP4 239.252.80.5/1b=AS:375t=0 0a=xbroadcastcontrol:RTSPm=video 5004 RTP/AVP 96b=AS:248a=rtpmap:96 MP4VES/90000a=control:trackID=1a=cliprect:0,0,240,320a=fmtp:96 profilelevelid=1;config=000001B0F3000001B50EE040C0CF0000010000000120008440FA285020F0A21Fa=mpeg4esid:201m=audio 5006 RTP/AVP 97b=AS:127a=rtpmap:97 mpeg4generic/44100/2a=control:trackID=2a=fmtp:97 profilelevelid=1;mode=AAChbr;sizelength=13;indexlength=3;indexdeltalength=3;config=1210a=mpeg4esid:101
Typical receiver architecture
DVB-H receiverIP stream
IP Demux
A/V data decoding
RTP parsingh.264 decoding
AAC decoding
ESG handling
FLUTE/ALCparsing
FEC decoding
decompression(gzip)
ESGparsing
Bootstrap
File
XML
XMLparsing
ESGDatabase
tuner
Application
A/V player
Channel Selection
ESG presentation
IEEE
SAP
?
2.4-2.5 GHz
~5 GHz
IEEE 802.11
a,b,g,n
Wifi
IEEE3GPPQUALCOMMKorea AACDVB Consorsium
ETSIDVB Consorsium ETSI
Standardisation Group
?UDDIMPG
(Media Program Guide)
DABCBMS - ESGMPEG2-TS PSI/SI (T)
CBMS - ESG (H)
Programme Guide
&
Content Description
30
(source Qualcomm)
UHF
Mobile
EV-DO
MediaFlo
6
2 GHz
UMTS
EV-DO
MBMS
12-16 (MBS)12
(with 3 carriers)20 to 3020 to 30
Number of TV Broadcast Channels
(256kbits/s)
2.3 GHz
2.5 GHz
3.3 GHz
3.4-3.8 GHz
VHF or L-Band2.2 GHz MSSUHF or L-BandFrequence
Band
IEEE 802.16e
Mobile WiMAX
DAB Eureka 147
MPEG2-TS DAB/ETIDVB-T
DVB-T
MPEG2-TS
IP over MPEG2-TSTechnology
WiMAXT-DMBDVB-H
in S-BandDVB-T/H